There has heretofore been known a diagnosing apparatus for identifying the location of a fault in an electronic control system on a vehicle by reading a fault code that is recorded in an electronic control unit (ECU) incorporated in the vehicle. See, U.S. Pat. No. 5,491,631 (hereinafter referred to as “U.S. Pat. No. 5,491,631A”). According to U.S. Pat. No. 5,491,631A, in the event of a fault of a peripheral device connected to the ECU (1) of the vehicle, a self-diagnostic means (52) generates fault information and stores the generated fault information in a fault code storage means (53) (see, for example, column 13, lines 31-35). When the fault of a sensor (4A) as the peripheral device is detected, the self-diagnostic means (52) identifies the location of the fault (systematic fault details, etc.) by displaying an inspection procedure on a fault diagnosing apparatus (2), based on the fault information and the fault code, which serves to identify the fault information (see, for example, column 18, line 32, through column 22, line 38, and FIGS. 21 through 24).